Getting a little OT but slight excuse for some nitty-gritty.
IMO both “definitions” in previous post are ambiguous by omission. They facilitate a hygienic compromise(s). Whether by intention I have never quite decided.
IMEX, a factory employee communal “toilet” is typically an enclosed 2 part area, eg a row of (often tiny) individual cubicles + a multi-functional external portion servicing all cubicle exitees. 3 simple hygiene questions, – (a) has anyone ever encountered soap within a cubicle ? (b) has anyone ever seen anybody actually cleaning / washing the components which activate flushing mechanisms within a cubicle / included within a SOP ? © has anyone ever encountered a toilet hygiene NC event due to an unannounced audit ? My answers would be 3 x No, not yet applicable.
The cautionary tales associated with (b)-type factors, eg cubicle door handles are of course legendary and sometimes hilarious although relevant data analysis is less common.
Where paranoia takes over from hygienic reality has AFAIK never been quantitated.
Neither of the definitions in post #2, as far as I can see, directly answers the OP except by an implied acceptance of something like (a) as below. I cannot remember ever having seen an actual minimum dimension quoted anywhere. It probably doesn’t exist. IMEX I have seen anything from (a) near-zero distance > a bootwash step > (near zero) a plastic separation curtain up to (b) initial walkways of a few, probably random, metres. Both scenarios have never seemed to cause any auditorial comments.
Would be an interesting topic for a thesis though.
Rgds / Charles.C